Observations

Description

Valves are lanceolate and narrow gradually to weakly protracted acutely rounded ends, or apices narrow abruptly to form protracted, subcapitate ends. The axial area is narrow and widens gradually to a small, more or less rhombic central area. The raphe sternum and central nodule appear raised in relief. The central nodule is half again wider than the raphe sternum and has flat or occasionally concave sides. The raphe is weakly lateral and nearly straight along the valve midline. Proximal raphe ends are nearly straight and relatively close together. Raphe pores are distinct and deltoid in shape. Terminal raphe fissures are hooked, the hooks opening toward the secondary side. The striae are strongly radiate throughout and become parallel only at the poles. Areolae in the striae are distinct and number 24-27 in 10 µm.

Original Description

Original Description

Valves lanceolate, gradually narrowing to weakly protracted acutely rounded ends, length 40-64 microns, breadth 9-10 microns. Raphe slightly sinuous, weakly lateral with distinct central pores in a comparatively narrow position. Axial area (very) narrow distally widening gradually to a small central area with various outlines due to some irregularly shortened median striae. Striae rather strongly radiate, some short ones in subpolar position parallel or very indistinctly convergent, 10.5-12/10 microns; lineolae arranged as in Navicula concentrica but less coarse than in that species, c. 27-29/10 microns. SEM (Fig. 30: 12): Sternum relief-like prominent on the valve outside, expanded in the centre. Central pores short, drop-like, not hooked and only slightly deflected to the secondary valve side.

Original Images

Cite This Page: Bahls, L. (2011). Navicula subconcentrica. In Diatoms of the United States. Retrieved February 21, 2018, from http://westerndiatoms.colorado.edu/taxa/species/navicula_subconcentrica

Navicula subconcentrica has lanceolate valves that are less than 11 µm wide. Valve ends are narrow and acutely rounded, to subcapitate. The proximal raphe ends are nearly straight and relatively close together. The central nodule is typically symmetric, with flat or slightly concave sides.

Compare

Navicula flatheadensis has larger valves with wider, weakly protracted apices. Proximal raphe ends of N. flatheadensis are more distant and deflected to the primary side of the valve. The central nodule of N. flatheadensis is typically asymmetric and convex on one side. Navicula pseudolanceolata has less attenuated apices and more distantly spaced proximal raphe ends than N. subconcentrica.